This invention, which was made under a contract with the U.S. Department of Energy, relates to titanium diboride powder and, more particularly, to a method for purifying such powder.
Titanium diboride (TiB.sub.2), an extremely hard refractory solid with very high resistance to oxidation and very low electrical resistance, is commonly commercially produced by the carbothermic reduction of a mixture of the oxides of titanium and boron. The TiB.sub.2 product from this process is always contaminated with oxides. Another method for producing TiB.sub.2 involves chemical vapor deposition from a mixture of titanium tetrachloride (TiCl.sub.4), boron trichloride (BCl.sub.3), and hydrogen (H.sub.2) on a hot surface. This method produces macrosize crystals of pure TiB.sub.2 which must be mechanically ground into powder and which consequently become contaminated, usually with metal oxides (Al.sub.2 O.sub.3,SiO.sub.2) from the grinding apparatus. It is suspected that this oxide contamination has a deleterious effect on the sintering of the powders and furthermore on integrity of sintered products.
Modifications to existing processes that would result in the direct production of pure TiB.sub.2 powders could be costly. It is therefore desirable to have a method for removing oxide contamination from TiB.sub.2 powders produced by existing processes.